one circle has aradius of 4 and the other 1meet at apoint P. rotate the circles asfixed units so thatthey rest on the horizontal.draw perpendiculars from eah center to the horizontal. a second horizontal at the center of the smaller.center to center you have 5 units. vertical distance between centers is 3 soyou have a 3,4,5 right triangle with 4 being AX